Multiducted electromagnetic pump

ABSTRACT

AN APPARATUS FOR PUMPING CONDUCTIVE LIQUIDS IS DESCRIBED WHICH COMPRISES A SINGLE TOROIDAL ELECTROMAGNETIC PUMP STRUCTURE WHEREIN THERE ARE A PLURALITY OF PUMP PASSAGES WITH EACH PASSAGE HAVING A TWO PUMP DUCT SANDWICH THEREIN. EACH PUMP DUCT HAS ASSOCIATED THEREWITH A PLURAL TUBE HEADER ASSEMBLY CONNECTED TO ITS INPUT AND OUTPUT PORTIONS. EACH TUBE OF THE PLURAL TUBE HEADER ASSEMBLIES IS ELECTRICALLY INSULATED FROM ADJACENT TUBES THEREBY MINIMIZING THE BYPASS CURRENT FLOW. CURRENT FLOW THROUGH EACH TWIN PUMP DUCT COMBINATION IS IN A COUNTER FLOW ARRANGEMENT TO MINIMIZE FIELD DISTORTION. THE SINGLE TOROIDAL PUMP STRUCTURE MAY THEREFORE COMPRISE ANY CONVENIENT NUMBER OF INDIVIDUAL PUMPS FORMED WITHIN THE COMPACT CONFIGURATION.

March 2, 1971 T. o. PAINE 3,567,339

I ADMINISTRATOR OF THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION vMULTIDUCTED ELECTROMAGNETIC PUMP Filed April 16, 1969 2 Sheets-Sheet IWWW I I r I March 2, 1971 1:0. PAINE 3,567,339

ADMINISTRATOR OF THE NATIONAL AERONAUTICS ANDSPACE ADMINISTRATION.MULTIDUCTED ELECTROMAGNETIC PUMP Filed April 16, 1969 r 2 Sheets-Sheet2 Patented Mar. 2, 1971 3,567,339 MULTIDUCTED ELECTROMAGNETIC PUMP T. O.Paine, Administrator of the National Aeronautics and SpaceAdministration, with respect to an invention of Jerry P. Davis, LaCanada, and Gerald M. Kikin, Pasadena, Calif.

Filed Apr. 16, 1969, Ser. No. 816,733 Int. Cl. F04b 19/00 U.S. Cl.417-50 Claims ABSTRACT OF THE DISCLOSURE An apparatus for pumpingconductive liquids is described which comprises a single toroidalelectromagnetic pump structure wherein there are a plurality of pumppassages with each passage having a two pump duct sandwich therein. Eachpump duct has associated therewith a plural tube header assemblyconnected to its input and output portions. Each tube of the plural tubeheader assemblies is electrically insulated from adjacent tubes therebyminimizing the bypass current flow. Current fiow through each twin pumpduct combination is in a counter flow arrangement to minimize fielddistortion. The single toroidal pump structure may therefore compriseany convenient number of individual pumps formed within the compactconfiguration.

ORIGIN OF THE INVENTION The invention described herein was made in theperformance of work under a NASA contract and is subject to theprovisions of Section 305 of the National Aeronautics and Space Act of1958, Public Law 85-568 (72 Stat. 435; 42 USC 2457).

BACKGROUND OF THE INVENTION (1) Field of the invention This inventionrelates to fluid pump systems and more particularly to direct currentelectromagnetic pumps capable of pumping conductive fluids.

(2) Description of the prior art The basic principles behind theoperation of DC electromagnetic pumps are well-known and involve theapplication of Faradays Law. In general, a conductive liquid flowsthrough a thin-walled tube of metal of high electrical resistivity.Conductive bus bars are attached to opposite sides of the tube, and theassembly is placed between the poles of an electromagnet. Currententering through the tube wall traverses the liquid in the tube anddevelops a longitudinal thrust therein.

Direct current electromagnetic pumps have found their most significantuse in power conversion systems which utilize liquid metals as reactorcoolants. Conventional electromagnetic pumps have a C-shaped magnetstructure surrounding a single flow channel. The magnet is generally theheaviest component in the system. Therefore, the use of such directcurrent electromagnetic pumps has been restricted by weight requirementsin such applications as metal cooled space power conversion systemswhich often require a large number of separate pump channels. Whileweight requirements may not be as significant in connection with groundbased installations, the power required to energize the large number ofelectromagnets associated with prior art plural pump installations hasheretofore restricted their usefulness.

Another disadvantage of conventional DC electromagnetic pumps resultsfrom the fact that the magnetic field produced by the flow of currentacross the pump tube distorts the field between the magnetic poles byintroducing a component which increases the resultant field intensity onthe upstream end and decreases it on the downstream end. Thisinhomogeneity in the field along the length of the tube produces agreater counter E.M.F. in the moving liquid on the upstream end than onthe downstream side with the result that the current distribution alongthe length of the tube is not uniform but is increased downstream andreduced toward the upstream end. Thus, the resultant current and fielddistribution is such that the regions of highest current density are inregions of lowest field intensity resulting in a significant lowering ofthe pumping capacity. One prior art technique for compensating for thiseffect utilizes an opposing field produced by an equal current flowingin the opposite direction in a conductor which is located above and/orbelow the pump tube. This method of compensation, however, has thedisadvantage that the magnetic gap must be considerably increased toprovide room for the compensating bus bars, thus significantlyincreasing the power requirements for generating the electromagneticfield. A second prior art method involves tapering the magnet poles sothat the magnetic gap is wider toward the upstream end. In addition, thetube cross sectional areas have been tapered so that the velocity of theliquid increases in the downstream direction at a rate such that thecounter in the liquid remains constant as the liquid traverses theregion between the poles. This second method suffers from the increasedhydraulic losses resulting from a tapered tube configuration andincreased tube fabrication difiiculties.

A further limitation upon the prior art devices results from thesignificant bypass current flow characteristic of prior art devices.Bypass current flow represents current that by-passes the pump duct andthereby represents power loss.

OBJECTS AND SUMMARY OF THE INVENTION This invention obviates theabove-mentioned shortcomings by providing a plurality of electricallyindependent liquid metal pumps of minimum weight utilizing a singlecommon magnet structure. The magnet structure has a plurality of gapslocated therein equal to one-half the total number of individual pumpsrequired. Within each gap there is located a symmetrical two pump ductsandwich wherein the ducts are electrically isolated from each other andfrom the magnetic pole faces by suitable insulation. A magnet copperwinding is associated with each pump duct and may be in electricalseries connection therewith. Bus bars are disposed on opposite sides ofeach pump duct. Current is caused to flow in each pump duct sandwich ina counterflow arrangement to minimize magnetic field distortion.

A plural tube header assembly is attached to the inflow and outflowportion of each pump duct. Each tube in the header assembly iselectrically isolated from all adjacent tubes to minimize the bypasscurrent flow. The common magnet structure can accommodate any reasonablenumber of pump circuits necessary for a given system and hence can becustom fabricated to meet the exact needs of particular systems withoutloss of efiiciency. The large number of individual pumps of the priorart, each having individual magnets, are replaced by 9 single magnetcompact design wherein magnetic flux losses and bypass current flowlosses are significantly reduced.

It is therefore an object of this invention to provide a pluralelectromagnetic pump apparatus of minimum weight.

It is another object of the present invention to provide a pluralelectromagnetic pump apparatus utilizing only a single magnet structure.

It is a further object of the present invention to pro- 3 vide anelectromagnetic pump having minimum magnetic field distortion.

Still another object of the instant invention is to provide anelectromagnetic pump apparatus having minimum bypass current flowlosses.

Still other objects, features and attendant advantages of the presentinvention will become apparent to those skilled in the art from areading of the following detailed description of several embodimentsconstructed in accordance therewith taken in conjunction with theaccompanying drawings and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of atoroidal pump structure constructed in accordance with the presentinvention;

FIG. 2 is a perspective view of one of the two pump duct subsections ofFIG. 1;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a perspective view of an elementary pump duct section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings,FIG. 1 shows a single toroidal pump structure 25 which actuallycomprises 40 individual pumps 1A, 13 to 20A, 20B formed into a cornpactring-shaped configuration. The ring structure is subdivided into 20symmetrical subsections with each subsection being comprised of a twopump duct sandwich as will be described hereinafter.

Referring now to FIG. 2, there is shown a typical two duct pump sectioncomprising symmetrical pump pair 10A and 10B. Pump 10A comprises atransmission tube 61 which is connected to a transition section 55.Transition section 55 connects transmission tube 61 to a five flattenedtube header assembly IOA which is welded to the rectangular crosssection pump duct 44. Each tube 1GA 10A of the header assembly A iselectrically insulated from adjacent tubes by a layer of suitableinsulation material such as alumina. The insulation serves to preventbypass current flow in the area adjacent to the pump ducts. Conductiveliquid is pumped in pump duct 44 into a second five flattened tubeheader assembly 10A then through a second transition section to a secondtransmission tube (not shown). The structure of pump 10B is identical tothat described above for pump 10A.

A magnetic copper coil 50 containing a suitable number of windings iswound around magnetizable material 30 in series electrical connectionwith copper bus bar 46. A second copper winding coil 51 is connected inseries electrical connection to copper bus bar 47, associated with pumpduct 84. Bus bars 46 and 47 are, as shown, disposed on each side of pumpducts 44 and 84 respectively, 50 as to make electrical connectiontherewith and therethrough with the electrically conductive fluid. Asshown, the current in bus bar 46 and therefore in pump duct 44- iscaused to flow opposite to that in bus bar 47 and pump duct 84. Thiscounter flow arrangement serves to minimize armature reaction effectsand results in opposite liquid flow as will be explained in greaterdetail later.

Referring now to FIG. 3, there is shown a cross-sectional view of thedual pump duct configuration of 'FIG. 2. Magnetizable material 30 isseparated from pump ducts 44 and 4.5 by layers of insulation material 40and 42 respectively, which layers may be fabricated from any suitabletemperature resistant insulation material such as alumina. Ducts 44 and84 are separated and electrically insulated from each other by a layerof alumina insulation 41. Insulation layer 41 also serves to insulateheader assembly IOA from header assembly 10B as shown in FIG. 2, thusassuring that pump channel 10A and 10B are electrically isolated.

Although the preferred embodiment has thus far been described as havingthe magnet field windings in electrical series connection with the pumpducts such is not a requirerment. The field and duct circuits may beisolated and separately supplied if such control is desired.

Referring now to FIG. 4, there is shown an elementary representativepump duct section 44 of width r, height s and length l.

The direction of the magnetic flux field B and current rfiow I is asindicated. The relation between the total current I flowing through theelementary pump duct section and the various electrical characteristicsof the elementary pump duct section 44 may be obtained from the standardDC electromagnetic pump design equation:

I= ymwuw +1.

where E =the counter-electromotive force developed in the liquid as itmoves through the magnetic field.

R the resistance of the bypass path through the tube wall.

.R =the resistance of the elfective current path through the liquid.

R =the resistance of the bypass path in the liquid.

rI =the current traversing the liquid 'which lies in the strong magneticfield.

The relation between the liquid metal flow and the various circuitperimeters may be likewise determined from the standard design equation:

10 s R R 10ps where:

B R..+R., B

Q=liquid metal flow, p=pressure rise B flux density s=fluid channelheight in the pump duct. Rearranging and solving for I gives:

( wan equals effective resistance for all current bypass paths andP=fluid pumping powen=I E One of the main pump design criteria isminimum current consumption at fixed pumping power Pf- Therefore,Equation 3 may be difierentiated with respect to E Solving for E gives:

E (min. current) [P (R l-R)] (5) Substituting Equation 5 into Equation 3gives:

1/ u R )1 L R (6) b o duet R where r is obtained from the above-notedreference. For the range of Ur of interest, r is closely approximated byr -=1 1.8K

where Substituting values for R and R into the equation for ductresistance gives In order to reduce bypass current paths, an inlet andexit tube configuration, as shown in FIG. 2 is utilized. As abovedescribed, the inlet and exit flow headers such as 10A are formed ofplural flattened tubes which are separated by electrical insulationmaterials such as alumina. Substituting equations 9, 8, and. 7 intoequation 4 gives in terms of E and s the magnetic flux density, B isB=8.33x10- sE (11) Equations 11, 10, 6 and 5 may now be used to designvarious pumps with K and s as variables.

The magnetic flux density in the pump duct is limited by the maximumflux obtainable in the magnetic structure, and the flux fringing factorThe relationship be tween the duct areas and associated fluxes is givenby A B =A B r (12) where:

A =the magnet cross sectional area A =the duct cross sectional area B=the magnet magnetic flux B =the duct magnetic flux The maximum fluxdensity available in any magnetic alloy is temperature limited. As iswell known in all cases the magnet must be operated below its Curietemperature to maintain useful magnetic properties. Therefore themaximum operating temperature anticipated to be experienced by themagnetic structure provides a design limit on the maximum achievablemagnetic flux.

OPERATION As illustrated in FIG. 1, the single toroidal pump structure25 is adapted to provide a plurality of individual pumps 1A, IE to 20A,20B formed into a compact ringshaped configuration utilizing only asingle magnet 30. The magnet copper windings, which are in series withan associated pump duct, receives a current which serves both to createthe magnetic flux field and provide a current flow through the liquidmetal in the pump duct. The liquid metal flows to each pump through anassociated transmission tube thence through an associated five flattenedtube header assembly to the associated pump duct section. While in thepump duct section, the interaction of the magnetic flux field with thecurrent flowing in the liquid metal causes an associated thrust to begenerated which has the eflect of pumping the liquid metal through theduct section. The exiting liquid metal flows through another fiveflattened tube header then through a second associated transition piecefinally returning to the system transmission tubing. Each two pump ductsandwich 1A, 1B to 20A, 20B has counter-flowing electrical duct currentthus effecting opposite pumping thrusts. Electrical insulation betweeneach tube of the five flattened tube header assemblies effectivelyreduces the bypass resistance losses. Various modifications to thepreferred embodiment will be apparent to those skilled in the artwithout involving a departure from the spirit of the scope of myinvention.

What is claimed is:

1. A direct current electromagnetic pumping apparatus for individuallypumping a multiplicity of independent streams of electrically conductivefluid, said apparatus comprising:

a plurality of electromagnets aligned along a circular axis, a pluralityof evenly spaced passages extending between adjacent electromagnets, themagnetic flux of respective electromagnets being directed through saidpassages in the same circular direction; a pair of electricallyconductive conduits positioned in each of said passages, each conduitpermitting the flow of electrically conductive fluid therethrough;

and

electrical conductor means, situated on opposite sides of each of saidconduits for directing the flow of electrical current through saidconduits, and the electrically conductive fluid contained therein, in adirection orthogonal to both the flow of fluid and the magnetic fluxdirected through said passages.

2. The apparatus of claim 1 wherein each of said electrically conductiveconduits has an inlet port and an outlet port, said apparatus furthercomprising:

first and second plural tube header assemblies respectively connected toeach of said inlet and outlet ports of each of said conduits, each ofsaid header assemblies having a plurality of tubes, and means forelectrically insulating adjacent tubes.

3. The apparatus of claim 2 wherein each of said electromagnets includesa core and a coil wound on said core, the ends of each coil beingconnected to the electrical conductor means associated with the conduitspositioned adjacent the ends of the core associated with said coil, saidapparatus further including means for electrically insulating said pairof conduits, positioned in each of said passages, from each other andfrom the core of adjacently situated electromagnets.

4. The apparatus of claim 3 wherein each coil is in electrical seriesconnection with the electrical conductor means connected thereto.

5. The apparatus of claim 4 wherein each conduit has a rectangular crosssection, the width of said conduit cross section being substantiallyequal to the width of said toroidal cross section.

'6. The apparatus of claim 4 wherein the wall portions of said conduitsare fabricated from a relatively high resistivity material.

7. Apparatus for pumping electrically conductive fluid comprising:

a magnetic structure having at least one passage extending therethrough,said magnetic structure directing magnetic flux through said passage;

first and second conduits positioned in said passage;

electrical conductor means extending lengthwise along oppositelydisposed sides of each of said conduits so as to make electricalconnection therewith and therethrough with the electrically conductivefluid;

a layer of electrical insulating material between said first and secondconduits;

means applying a current to said electrical conductor 'means forproducing a current flow in said first conduit which is opposite to thecurrent flow in said second conduit;

first and second plural tube header assemblies connected to the inletand outlet portions, respectively, of each of said conduits with each ofsaid tubes being electrically insulated from adjacent tubes, whereby thebypass current flow through said apparatus is minimized;

means for electrically insulating said first and second plural headerassemblies associated with said first conduit from the first and secondheader assemblies associated with said second conduit; and

first and second magnetic winding coils, said first winding coilassociated with said first conduit, said second winding coil associatedwith said second conduit, said winding coils directing magnetic fluxthrough said conduits in a direction substantially perpendicular to theflow of fluid, said winding coils being wound abount the magneticstructure.

8. The apparatus of claim 7 wherein each magnetic winding coil is inelectrical series connection with the 75 electrical conductor means ofits associated conduit.

9. The anparatus of claim 8 wherein the magnetic Referenis Citedzirc'astgtglggtignlm the shape of toroid having a rectangular UNITPDSTATES PATENTS it). The apparatus of claim 9 wherein each of said con- 1323 5 55 duits has a rectangular cross section, the width of said 5 510/1966 R065 103 1 conduit cross sections being substantially equal tosaid toroidal cross section. ROBERT M. WALKER, Primary Examiner

